Node:Defining New Types (Smobs), Previous:How Guile does it, Up:Data Representation
Smobs are Guile's mechanism for adding new non-immediate types to
the system.1 To define a new smob type, the programmer provides Guile with
some essential information about the type -- how to print it, how to
garbage collect it, and so on -- and Guile returns a fresh type tag for
use in the first word of new cells. The programmer can then use
scm_c_define_gsubr to make a set of C functions that create and
operate on these objects visible to Scheme code.
(You can find a complete version of the example code used in this
section in the Guile distribution, in
directory includes a makefile and a suitable
main function, so
you can build a complete interactive Guile shell, extended with the
datatypes described here.)
The term ``smob'' was coined by Aubrey Jaffer, who says it comes from ``small object'', referring to the fact that only the CDR and part of the CAR of a smob's cell are available for use.